The Bureau of Mines has developed a cryogenic heat transfer method of controlling wastebank fires. A slurry of liquid n2 and granular co2 is used as the heat transfer medium. Because of its extremely low temperature (-180 deg c), the cryogenic slurry absorbs large quantities of heat. Changes in state from the solid and/or liquid to the gas phase also absorb heat. The phase change produces over a 500-fold increase in volume, creating a cold pressure wave that moves isotropically away from the injection point. The cold wave absorbs heat, produces an inert atmosphere, and forces smoke and fumes from the combustion zone to the surface. Thus, the injected slurry causes a relatively quick cooling of the burning material, while the expansion of the evaporating gas maintains the cool atmosphere for an extended period. The movement of the inert gas is controlled by pressure and buoyancy. To evaluate limiting parameters and operating conditions, the Bureau has conducted injection and heat transfer tests. It is currently developing specifications for a full-scale test to control a wastebank fire with a cryogenic slurry of liquid n2 and granular co2. Preliminary estimates indicate that the cost of injecting a cryogenic slurry is comparable to the cost of more conventional control methods for abandoned mined land fires.